Typical automotive engine-cooling fan assemblies include an electric motor having a driveshaft coupled to a fan. The typical fan includes a hub which extends from the driveshaft to the roots of fan blades extending from the hub. The hub typically has a face portion which extends radially outwardly from the driveshaft attachment to a cylindrical portion to which the fan blades are attached. To conserve axial space, the motor is typically positioned on the concave side of the hub such that at least a portion of the motor is within the cylindrical portion of the hub. An opposite or a convex side of the hub guides air toward the fan blades.
Radial ribs are incorporated with the hub to stiffen the fan structure. Centrifugal forces on the fan blades and the rotating band (if one is used) tend to deform the hub. This effect can be decreased by placing ribs on an interior surface of the face portion and on an interior surface of the cylindrical portion. If a ventilated or air-cooled motor is employed, the ribs may also help cool the motor. The region between the face of the motor and the face of the hub, including the ribs, acts like a centrifugal fan to pull cooling air through the motor.
FIGS. 1-3 illustrate a prior art automotive engine-cooling fan assembly 10. The prior art fan assembly 10 includes a fan 14 mounted to a driveshaft 18 of a motor 22, which is supported by a fan shroud 26. The fan shroud 26 is positioned adjacent a heat exchanger 30 (e.g., a radiator), such that rotation of the fan 14 generates an airflow A1 through the heat exchanger 30. The fan 14 includes a hub 34 coupled to the driveshaft 18 for rotation with the driveshaft 18. The fan 14 also includes a plurality of blades 38 radially extending from the hub 34.
FIGS. 1 and 2 illustrate a plurality of radially-extending ribs 42 attached to an interior surface 46 of the hub 34. The ribs 42 attach over their entire extent to the interior surface 46 of the hub 34 and the ribs 42 are evenly distributed about the hub 34 to structurally reinforce the hub 34.
The ribs 42 axially extend toward the motor 22 to within a running clearance of the motor 22. The ribs 42, upon rotation of the fan 14, function as a centrifugal fan to generate an airflow A2 through the motor 22, which is air-cooled and ventilated through apertures 48.